Resistor control mechanism



Jan. 8, 1935. E. G LODGE 1,987,118

RESISTOR CONTROL MECHANI SM Filed Aug. 26, 1931 3 Sheets-Sheet l .mag/6.

Jan. 8, 1935. E. G. LODGE 1,987,118

- RESISTOR CONTROL MECHANISM Filed Aug. v2'55, 1931 5 Sheets-Sheet 2 IHNINIIIllllllllliHMIIIWIIIIIIIIIIlNINIIIIIHININIINI Jan. 8, 1935. E LODGE y i REsIsToR CONTROL ncmmrsu Filed Aug. 26. 1951 3 Sheets-'Sheet 3 Patented Jan. 8, 1935 RESISTOR CONTROL MECHANISM Edmund G. Lodge, Oak Lane, Pa., assignor, by

mesne assignments, to Chicago Telephone Sup- 11111151 Company, Elkhart, Ind., a corporation o! ana Application August 26,

7 Claims.

My invention relates to variable resistors believed to have their widest application in circuits of radio receiving sets, circuits of microphones y and the like, and frequently comprising volume control units of loud speaker circuits.

One purpose of my invention is to provide structure of the character indicated that will be at once well suited to the needsof service and adapted to easy and inexpensive manufacture.

A further purpose is to wrap a spaced turn resistor element about a ceramic mount.

A further purpose is to prevent the individual turns of a resistor wire wound upon a core from movements along the core when or if the core shrinks in aging.

A further purpose is to use any shrinkage of the core of a wire-wound resistor element to more firmly clamp the individual turns of the element between the core and a mount thereof, thereby using core shrinkage to insure -permanence of the spacing between the turns and of the placement of the turns along the core where hitherto core shrinkage has upset the permanence of the turns in both particulars.

A further purpose is to make the core of a spaced turn resistor element of material that will gradually contract with aging in order to insure more firm connection between the element and its mountor the element and an electric terminal,

either or both.

A further purpose is to secure a low resistance gradient along one portion'of a wire-wound resistor by clamping an electrical connection transversely across the turns of said portion suitably inwardly from the contact edge of the resistor, using the clamping connection between the resistor and its mount to maintain good contact between the said connection and the adjacent wires.

This electrical connection may be inside the resistor winding adjacent the core or outside thereof adjacent the mount, may be a ne wire parallel to the edge of the resistor, the resistance of the wire providing the low resistance gradient, or it may comprise a conducting sheet of ,progressively varying distance from the contact edge of the resistor formed to by-pass the turns along the length of the sheet and connecting to the movable contact member through progressively variant portions of the uncoated turns, according to the position of the contact member along the resistor.

A further purpose is to provide desirable and novel connections mechanical and electrical between the contact members of a resistor of the character indicated.

A further purpose is to combine a ceramic 1931, Serial No. 559,588

ages to tighten the connection between the element and its mount.

A further purpose is to provide a variable resistor of the type indicated with a contact plate at once effective as a contact member and as an optional alternative operator of a second resistor unit or of an external switch.

A further purpose is to extrude ceramic material into a tubular section of optionally indeflnite length and having preferably lateral T slots, cutting the length into short sections and firing to provide ceramic mounts for resistor strips.

A further purpose is to secure a resistor element to the periphery of-a ceramic mount by bolts anchored in lateral T slots of the mount.

A further purpose is to use a bolt clamping an end ofl a resistor element to the periphery of a ceramic mount at a T slot of the mount, the bolt inwardly anchoring in the slot as an electrical connection between the resistor and a terminal to an external electrical circuit, preferably threading the inner end of the bolt through an` inner portion of the terminal extended into the slot.

A further purpose is to provide a desirable form of preferably soldered clamp connections between the ends of a wire-wound resistor element and a preferably ceramic mount of the element, optionally using the clamps as terminal connections of the resistor.

Further purposes will appear in the specification and in the claims.

I have elected to show one main form and detail modification thereof only of the many different forms of my invention, showing however, a main form that is practical and eflicient in operation and which well illustrates the principles involved.

Figure l is a top plan view of structure embodying important features of the invention, the view showing a variable resistor unit without a cover that may comprise a mere closure for the casing, a mount for a switch opened and closed automatically by the setting movement of the resistor unit coupled to the first, or another resistor.

Figure 2 is a section taken upon the line 242 of Figure 1 with some of the central members not sectioned.

Figure 3 is a fragmentary view corresponding to a portion .of Figure 2 except that some of the detail members unsectioned in Figure 2 are shown sectioned in Figure 3.

Figure 4 is a detail section taken upon the line 4-4 of Figure 1 in the direction of the arrows.

Figure 5 is a plan view of a detail comprising a desirable form of mount for the resistor element.

Figures 6 and 7 are plan views of different details. A

Figure 8 is a fragmentary section taken upon the line 8 8 of Figure l.

Figure 9 is a fragmentarysection corresponding to Figure 8 but showing a detail modification.

Figures 10 to 13 are fragmentary views corresponding generally to Figures 8 and 9 but showing modiiications with respect to a minor detail. Figure 14 is a fragmentary section taken upon theline 14-14 of Figure 13.

Figure 15 is a view corresponding to a portion of Figure 2 but illustrating a detail modification.

Figure 16 is a side view of an unmounted resistor element for use in the disclosed unit.

Figure 17 illustrates a desirable modiiication for use when a low resistance gradient along a selected portion of the resistor, is desired to be lower than is adapted to be obtained easily with the form of resistor shown in .Figure 16.l u

Figures 18 and 19 are cooperating details of a modified resistor unit for obtaining any desired low resistance gradient.

Figure 20 is a detailA corresponding to Figure 19, modified from 19 merely with respect to the difference in resistance gradient.

Figures,21 to 24 inclusive are side elevations partly sectioned, showing the structure of Figure 2 combined alternatively with dilerent end closure members, each of which may be in some cases preferable to the others.

Figure 21 shows a simple closure, Figure 22 a closure ,including a switch, Figure 23 a closure including a second resistor unit and Figure 24 includes the structure of 23 combined with a third unit generally similar to that of Figure 22.

Figure 25 is a detail perspective.

Figure 26 is a detail section on the line 26-26 of Figure 22.

Like numerals refer to like parts in all iigures.

Describing in illustration and not in limitation and referring to the drawings:-

Referring to Figures 1 to 15, numeral 10 refers to the resistor element which issupported by an insulating formed block 11, the block being desirably of ceramic material.

In the construction shown, the block 11 is preferably formed by extrusion, desirably ceramic material cut to length after extrusion and then iired.

Longitudinal recesses formed during the extrusion process include central and oiiset perforations 12 and 13 and radially inward T slot openings 14 and 15.

The central perforation 12 receives a metallic bushing 16 that mounts and rigidly connects the block 11 to the casing 17 and gives bearing support to a turn shaft 18 carrying a movable contact plate 19.

The bushing 16 carries a nut 20 outside thecasing, is externally threaded at 21 to take the. A nut, .is bored longitudinally to iit the turn shaft 18, and is counterbored at 22 at its inner end to permit its more easy fianging at 23 over a station` ary terminal plate 24.

The casing 17, insulation sheet 25, which is suitably paper,and block 11 and terminal plate 24 are assembled upon the bushing above the ange 21 at the end of the threads 21, and then clamped into a unit by turning over the counterbored end of the bushing at 23.

Angular registry of the casing 17, block-11 and terminal'plate 24 is secured by an upward lug 26 and-a downwardY lug 27 that respectively t into the upper and lower ends of the perforation 13 ofthe block 11. Desirably the terminal plate 24 is serrated 'at 28around the bore passing the bushing 16, therebyproviding an angular lock- The T slot openings 14 and 15 serve to anchor the ends of the resistor element 10 and terminals therefrom to the mount 11. l

Two main types only of the different anchor connections are shown, these types including re#- spectively screw and spring clamp connections.

The screw type of anchor is best seen in Figures 8 and 9.

In the anchor connections of Figures 1 and 8, inwardly extending screws or bolts 29 strongly clamp the ends of the resistor 10 to the outside of the ceramic mount and the terminals 30 and 31 to the inwardlydirected shoulders of the T slots 14 and 15.

The head ends of the bolts 29 electrically connect with one or more of the adjacent resistor turns and the inner screw ends of the bolts thread the terminals which in turn are extended upwardly and outwardly through suitable perforations of an insulation space sheet 32 (suitably treated paper) and an opening 33 of the casing 17 to receive the end connections of the external circuit.`

'I'he extension of the terminals may be vertically up or down from the screw 29, up over the inner end of the block and out the lateral opening 33 of the block or down through an end opening 34 of the casing (Figure 9).

A few different forms of the clamp type of anchor are shown in Figures 10 to 14 respectively, any one of these forms being adapted to be combined with a screw clamp.

All of the clamps illustrated are of the U type.

The clamp terminals 35 of Figures 10 and 11 are passed upwardly from the lower side of the block with inner arms 36 clamping the inwardly directed shoulders of the block perforations 14- and 15, the outer arms 37 rst clamping the ends of the resistor 10 to the block and then extending outwardly through the spacer sheet 32 and casing opening 33 to receive the external connections, not shown.

It will be seen that in Figure 10 the thickness of the connecting portion 38 of the U clamp extends below the bottom line of the block 11 and in order to avoid an uneven seating of the block, an adequately thick auxiliary paper sheet 39 cut away at the connecting portions 38 of the clamp is placed under the block above the sheet 25.

, -In the alternative form of Figure 11 the bottom of theblock has been recessed upwardly at 40 to permit the connecting portions 38 of the U clamps to lie even with the bottom surface of the block.

Figures 12 and 13 illustrate that the U clamps may be passed downwardly from the upper side inner arms 36"l of the clamps are extended downwardly through a casing opening 41' and then outwardly to make connections with the external circuit.

lDesirably the outer arms of the clamps are soldered to the adjacent turns oi.' the resistor wire and when the resistor wire is nichrome or any materlalunadapted to easy soldering it should be coated at the surfaces to be soldered with a metal such as copper adapted to more easy sol-l dering.

Desirably the outer arms of the clamps are perforated as indicated at 42, Figure 14, to make the solder connections more firm. v

It will be understood that the screw members such as shown at 29,Figures8 and 9 or in dot-anddash line at 43 Figure 12 may be used with any of the spring clamps to more strongly clamp the in ner and outer arms together and that when this is done the soldering may be optionally dispensed with, though it is usually preferable to-solder, the perforations 42 at the soldering connections being such as to suitably increase the hold between the solder and clamp.

If the screws 43V are not to be used the vT openings through the block at 14 and 15 may omit the lateral slot openings to the periphery.

However the radial abutments at these slot openings form desirable hold surfaces for inward projections from the ends of the resistor elements adapting the clamps to more easily hold the ends of the resistor element to place.

The resistor element 10 includes a high resistance wire 44, suitably of nichrome or the like, wound on an insulating and supporting core 45.

The turns of the wire 44 are preferably uniformly spaced along the core, the resistances of the successive individual turns being desirably modified along any portion or all of the length of the block to secure the desired predetermined total resistances at different turns of the element, that is to properly relate the range of resistance between the movable contact and a fixed terminal to the range of movement of the movable contact.

Selective modifying of the resistances ofindividual turns of the resistor element along the resistor unit is conveniently accomplished by suitably depositing low resistance metal, for example copper, over suitable portions of selected turns of the resistor, as disclosed and-claimed in a copending application, of Lodge and Da Costa, Serial No. 438,596, for Variable resistances, filed March 24, 1930, and which in itself forms no part of the present invention.

Frequently the resistor has desirably a succession of turns of relatively very low resistance along a portion 46 (Figure 16) near one or both ends, with turns of full resistance along a portion 4'7 spaced from the low resistance portion 46 and an intermediate resistance taper along a portion 48, the taper portion including turns that are of progressively decreasing resistance toward the low resistance turns, as indicated in Figure 16 where the low resistance coating is shown by stippled lines.

All of the turns are preferably left uncoated at portions 49 thereof closely adjacent the upper edge 50 of the unit where the turns are adapted to be engaged by the-slide contact 19 in that any corrosion at this surface has been found to result in noise if the resistor is used as a volume control of a loud speaker circuit.

It is sometimes desirable to provide a resistor unit having given dimensions and a given wire with a lower resistance gradient along a portion 46 (Figure 16) of the coil than may be readily obtained by merelycoating major portions of the individual turns with copper or the like while leaving all the turns uncoated at portions 49 thereof adjacent the contact edge of the coil. It will be seen that the added increment of resistance of a single turnis the sum of the resistances of the coated and uncoated portions of the turn and can therefore in no case be less 'transversely connecting the resistor turns tcgether along the desired low gradient portion of the element by a conducting member.

In Figure 1'7 this conducting member comprises a resistance wire 51 which may be an end of the same wire used winding the element, or may be a different wire, according to circumstance.

The wire 51 should make good electrical contact with the individual resistor turns of the low gradient portion of the element, and the clamping of the element against the block 11 insures this proper engagement between the transverse connecting wire 51 and the individual turns of the resistor.

It will be seen that whether the wire 51 is inside the winding or outside thereof it is transversely adjacent the individual turns of the winding so that when the element is clamped to the block ll each turn along the winding is pressed strongly against the conducting wire.

When the transverse conductor is a resistance wire the increment of resistance is due chiefly to the progressively variant length of resistance wire 51 in the circuit between the slide contact and a fixed terminal of the resistor.

The finer the wire 51, the greater will be the resistance gradient but this gradient will usually be very low and in any event lower than will be the ycase if the wire is omitted.

A wire 51 of given gauge and resistance characteristics may be used to obtain widely variant low resistance gradients by suitably varying the slope of the wire with respect to the edge of the element.

The conducting element transversely connecting the turns of the winding along the portion of the element that is to have a particularly low resistance gradient may comprise a conducting sheet 52 such as illustrated in Figures 19 or 20,

with the resistance of the sheet optionally negligibly small as compared to that of the individual turns of the windings.

In this arrangement the conducting sheet 52, whether inside or outside of the windings is pressed against the clamping of the element against the block and the distance from the slide contact 19 to the conducting sheet 52 progressively changes by reason of any selected slope of the upper edge 53 of the conducting sheet with respect to the edge 50 of the resistor unit.

If the slope is nearly horizontal, the gradient will be very low but if it is steeper, as illustrated for example by the sheet of Figure 20, the gradient will be greater.

The portions of the windings adjacent the sheet may or may not be coated with copper or the like.

It will be seen in the element shown in Figure 18 there is a taper along the space 54 correspondi ing to the gradient 48 of Figure 16, obtained by suitably copper plating the tapering portions of 'the turns, that along the space 55, the gradient of increasing resistance is due to the greater distance between the contact slide and the transindividual turns by the i verse sheet 52 as the member moves to the right.

At the right end of the sheet 52 the taper may again be obtained by coating with copper or the like as indicated by the stippledlines along the portion 56 of the'element.

'I'he transversely conducting member, whether sheet or wire may desirably be soldered to the turns of the resistor, as indicated at 57 of Figure 17, one or both of the soldered members being optionally coppered for more easy soldering.

The insulation core 45 of the resistance element 10 is preferably of insulation material that will continue to shrink duringaging as this avoids any danger of the connection between the resistance element l .and the. block 11 loosening with the passage of time.

Desirably the core 45 comprises a strip of incompletely cured Bakelite or other phenol condensation product, as curing and a resultant shrinking then continues after manufacture, causing the strip to bind the block more tightly as it ages, resulting in a permanence of the spacings and placements of the resistor turns and of effective electrical connections between the transverse conducting members 51 and 52 and the individual adjacent resistor turns.

Desirable features of the invention, some of them illustrated in alternative forms, are directed to electrical and mechanical details of the resilient slide contact 19, the turn shaft 18 carrying the contact and the connections between the movable contact and an external circuit.

The turn unit includes the shaft 18, plates 59 and 19 fastened to the inner end'of the shaft, and one or more spring washers 60 in a groove 61 at the outer end of the bushing 16 locking the shaft from inward movement.v A,

The outer end 62 of the shaft will normally carry a suitable insulation knob 63 for manipulating the unit.

The shaft 18 has bearing support in the main bushing 16 that holds the assembled'stationaryy members together as already described and the stop plate 59 and resilient contact plate 19 are mounted succesively on a noncircular (suitably triangular) projecting end 64 ofthe shaft, be-

ing angularly registered by fitting over the noncircular end shank 64 of the shaft and fastened to place by riveting the shank at 65.

Angular movement vof the turn unit is limited to its desired range by cooperating stops'66 and 67 respectively on the plates 24 and 59 and respectively comprising upward and radial lug projections, (Figures 6 and 7).

The resilient contact plate 19, conveniently die stamped from suitable resilient sheet material, includes a central portion 69, an outer portion 70 and a neck connection 71 between the inner and outer portions.

The central portion 69 radially overlaps the stop members 66 and 67 and carries an arcuate spring leaf 72 making a slide'resilient contact with the terminal plate 24 outwardly of the stops 66 and 67.

'I'he outer portion 70 includes a contact arm V73 and arcuate arms from opposite sides of the inner end thereof to the neck 71, the headV of the contact arm presenting a preferably downward-A ly convex surface to the upper edge of theresistor coil, the outer portion being formed to maintain strong downward resilient engagement with the edge of the resistor.

Opposite sides of the central portion are desirably recessed at 74 and 75 to adapt the plate to receive the prong ends 76 of a coupling 77 when the resistor unit is to cooperate with a second unit to form a dual volume control such as that indicated in Figure 23.

In the illustrated dual controlthe casing 17 of one unit may be the casing'of a single unit, the casing cover of the single unit being replaced by a suitably modified casing 78 of a second unit,

the two casings optionally differing one from' the other merely to an extent adapting the open end of one to t inside the open end of the other, with locking projections 79 of one casing fitting corresponding recesses 80 ofthe other casing.

In the illustration three terminals are shown from each unit. Obviously one or both of the resistor units of the'dual control, or of the single unit resistor may have either two or three terV minals according to circumstance.,

The plate 19 is desirably provided with a formation atthe neck side adapting it to easy mounting of switch-operating mechanism.

Asillustrated the plate is recessed at 81 and perforated at 82 and 83 near opposite sides of the recess.

An insulation mount 84 for a switch operating pin 85 is fastened by suitable rivets 86 to the plate 19, the rivets passing through the perforations 82 and 83. The object of the recess 81 is to provide clearance for the inner end of the pin 85 that projects upwardly for operating a suitable switch. f,

Normally the switch is thrown out whenthe turn unit is moved to its position of disuse and thrown in as the turn unit is movedto its range of use.

Structure embodying this is illustrated in Figure 22, where the pin 85 cooperates with resilient snap mechanism 87 controlling the position of a switch blade 88 with respect to contacts not ,shown but connected respectively to terminals 89 and 90 on the outside ofthe lid 91. It will be understood that the character of the switch may be widely varied and the indication is intended for a conventional one for any switch adapted to be operated by the pin projection 85 from the contact member 19.

The easy adaptation of the-plate 19 to permit the resistor to combine with a simple lid closure such as illustrated in Figure 21, with a switch closure such as illustrated in Figure 22 or with a second resistor to form a dual unit of Figure 23 is particularly advantageous from a manufacturing standpoint, permitting the same assembly to be used interchangeably with the different structures needed to meet different requirements -of the same or different customers.

The coupling lmember 77 of Figure 25 may be either fiber or an electrical conductor, according to circumstance. Normally in the dual unit of Figure 23 it will be of insulation material while in the triple unit such as that indicated in Figure 24 it may desirably be a conductor, particularly if the triple unit is for use as a T pad control.

In the latter event the three movable contacts for the three resistor coils of the unit may in practice be electrically connected while three terminals 92, 93 and 94, one from one end only of each resistor coil may be all that are required.

It will\be seen in the structure of Figure 24 the third resistor unit 95 and second resistor unit 96 have a common shaft 97. 'I'he second unit is coupled to the first as indicated in Figure' 23 with the single exception that the coupling member 77 may comprise an electric conductor instead of an .insulation member. Y

The outer member of the third unit may be closed with a lid carrying switch mechanism 98 that may be in every way similar to the lid and switch unit of Figure 22.

'I'he combination of ceramic or hard nonshrinking mount and resistor cores clamping their windings individually against the mount and with a force that tightens with any gradual shrinking of the core with aging avoids any possibility of longitudinal shifting of the windings of the resistors as the units age, and is particularly desirable in the plural unit resistors such as the dual volume control of Figure 23 or the threeunit T pad control of Figure 24.

It will be understood that a customer may specify quite ldefinite relations between the resistance ranges of the resistors of a plural unit and that any shifting of the resistor windings on any one of the resistors of the T pad control of Figure 24 for example, might readily to very considerable extent eliminate the value of the unit as a whole, even though windings of the other two resistors remained in their set positions.

'Ihe present invention in addition to its other advantages, eliminates the danger of the windings shifting under use which has hitherto been so troublesome in practice, and particularly troublesome with the plural resistor units of Figures 23 and 24. In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:-

l. A hard substantially non-shrinking block, a`

flexible resistor element comprising a strip of material adapted to shrink 'during aging and a resistance wire wound on the strip along a material portion of the length thereof in combination with means fastening the ends of the element to the block adapting the connection between the block and intermediate portion of the element to tighten during aging by the shrinking of the strip.

2. A ceramic block, a exible resistor element comprising a strip of material adapted to shrink during aging and a resistance wire wound on the strip along a material portion of the length thereof in combination with means fastening the ends of the element to the block adapting the connection betweenthe block and intermediate portion of the element to tighten during 881118 by the shrinking of the strip.

3. A hard substantially non-shrinking insulation b1ock,'a resistor element including a strip of incompletely cured phenol condensation product and resistance wire wound on and along the strip, the strip wrapping about a portion of the periphery of the block, and means fastening the ends of the strip tightly to the block adapting the shrinking of the strip during 381118 to ,tighten the connection between the block and strip.

4. A wire-wound resistor including a exible strip of insulation material, spaced turns of wire along the strip in combination with a ceramic mount having a non-central perforation partially surrounded by the strip, means fastening the strip to the periphery of the' mount adapting the intermediate portion of the strip to clamp the mount, a casing having a lug extending upwardly into a perforation of the mount and a terminal plate upon the upper side of the mount having a terminal arm extending laterally through the casing -and a lug extending downwardly into the perforation, the perforation registering the terminal plate, mount and casing angularly, and a central' tubular member clamping the plate, mount and casixig together and affording bearing support for a movable contact.

5. A ceramic mount for a wire-wound resistor including a generally circular block having a longitudinal perforation and lateral T slots along the length of the block respectively for mounting a turn shaft and for fastening the ends of the resistor element to the sides of the block and to electrical terminals of the element in combination with a wire-wound. resistor fastened thereto at the slots by fastening means between the resistor and block including a U clamp having clamping arms respectively inside`the slot and-outside the resistor, one of the arms being extended to form a terminal,

6. A wire-wound resistor including a flexible strip of insulation material, spaced turns of wire along the strip in combination with a hard mount, partially surrounded by the strip, means fastening the spaced ends of the strip to the side of the mount with the intermediate portion of the strip under longitudinal tension and by the said tension clamping the individual turns of wire against the mount along the outside periphery thereof, a terminal plate having an upward lug, a tubular bearing longitudinally through the mount and fastening the plate thereto, a turn shaft mounted in the bearing, a radial lug thereof adapted to engage the upward lug and thereby to limit the range of angular movement of the shaft, a plate mounted upon the shaft above the radial lug having spring portions simultaneously engaging respectively the upper edge of the resistor and the top of the terminal plate, said structure and a downward lug on the terminal plate registering in a longitudinal perforation of the block to relaterminal plate, a sheet of insulation material perforated to pass the terminal arm and an upward lug on said arm holding the sheet from inward movement along the arm.

7. A wire-wound resistor including a flexible strip of insulation material, spaced turns of wire along the strip, in'combination with a hard mount partially surrounded by the strip and means fastening the spaced ends of the strip to the side of the mount with the intermediate portion of the strip under longitudinal tension and by the said tension clamping the individual portions of wire against the mount along the outside periphery thereof, a terminal plate, acasing having a lateral opening, a tubular bearing fastening the plate, mount and casing together, laterally spaced terminals respectively from the said plate and from one of the ends of the resistor extending outwardly through the opening, a sheet of insulation material inside the casing at the lateral opening spacing the terminals, and a lug onthe terminals locking the sheet from inward movement.

EDMUND G. IQDGE. 

